This invention relates to electrical energy power supplies and more precisely, to specialized batteries which have special utility in packs or assemblies comprising a container holding self-developing film unit(s) integrated with an electrical power supply system.
U.S. Pat. Nos. 3,705,542; 3,543,662; 3,543,663, and 3,595,661 relate to photographic film packs comprising an enclosure containing self-developing film units integrated with a power supply system. Such film packs are presently employed exclusively in a photographic camera sold by Polaroid Corporation of Cambridge, Massachusetts, U.S.A. under the tradename "SX-70".
Essentially, film packs or cassette structures described in those patents comprise an opaque enclosure containing a dark slide for covering an exposure station in a forward wall of the container, a stack of individual "self-developing" film units positioned behind the dark slide, means for urging the stack of film units towards the forward wall to position the uppermost film unit in the stack in the exposure station and an electrical power supply system for operating electrical mechanisms of a camera designed for using the pack.
As disclosed in U.S. Pat. Nos. 3,750,551 and 3,760,701, when the film pack is inserted into the camera, the dark slide automatically is removed through a withdrawal slot at one end of the enclosure to uncover the exposure station and the uppermost film unit is urged into position in the exposure station by the means mentioned before which usually involves a spring biased platen.
A photographic cycle for the camera involves a somewhat complex series of operational events each imposing electrical power demands and each being controlled by an integrated solid state control circuit. As detailed in U.S. Pat. No. 3,774,516, this control circuit monitors several mechanical manipulations of the instrumentalities of the device involving a dual energization of a d. c. dynamoelectric motor as disclosed in U.S. Pat. Nos. 3,811,081 and 3,731,608 as well as a select multiple energization of exposure regulating tractive electromagnetic drives as described inter alia, in U.S. Pat. Nos. 3,791,278; 3,750,543; 3,805,204 and 3,820,128. The operational events carried out by the camera include those of securing an exposure chamber, reflex optical path conversion, exposure regulation of a film unit, motor driven film unit removal and processing as well as the noted automatic dark slide removal.
To power the camera throughout a series of the above-catalogued operational events, a battery power supply is required which exhibits a low internal impedance and is capable of providing a relatively high current output with multi-cycle capacity. During its powering activity, the battery is called upon to maintain the predetermined voltage levels required for operating integrated logic control circuits.
The "self-developing film" for such packs or cassettes is sometimes described as an integral negative-positive film unit having as essential elements, a photo-sensitive element having a photosensitive system for providing a diffusion transfer image, an image-receiving element, an opacification system and a rupturable container holding a processing composition. The elements are integrated such that upon distribution of processing composition within an exposed unit, a diffusion transfer image is provided in the image-receiving element which image is viewable against a reflective background without peeling the film unit apart. The film units are adapted for processing outside the camera since effective protection against further exposure is provided by way of the opacification system which in some integral negative-positive film units is integrated with the unit prior to exposure of the photosensitive system while in others, the opacification system is integrated with the unit after exposure. In the preferred integral negative-positive film units, the opacification system comprises a combination of light-absorbing dyes and a light-reflecting material or pigment and this combination is included in the rupturable container and distributed between the photosensitive and image-receiving elements after exposure. Further details relative to the integral negative-positive film units may be found in U.S. Pat. Nos. 3,415,644; 3,415,645; 3,415,646 and 3,647,437 among others.
A particularly desirable attribute of the noted camera-film system resides in the foldability of the camera component thereof into a thin, compact configuration suited for facile portage. The availability of such design compactness stems, in part, from the utilization of a flat battery structure in combination with the film cassette for the power supply of the camera. Of considerable importance to the system, however, by providing a battery which is discardable with an exhausted film cassette, the camera operator is assured of the presence of a fresh power supply upon each replenishment of a film supply to the camera. Essentially, the film pack contained power source has comprised a battery of the type described in detail in U.S. Pat. Nos. 3,543,662; 3,563,805; 3,617,387 and 3,734,780 among others. Such flat or planar batteries are primary batteries of the Le Clanche type including a zinc anode system, a manganese dioxide cathode system and an aqueous electrolyte of ammonium chloride, zinc chloride and usually a small amount of mercuric chloride. When the film pack is inserted into the camera, the battery integrated therewith is connected to the camera's electrical system to provide a power source of sufficient current capacity and evidencing requisite low internal impedance for operating the camera through a given number of cycles, for instance, ten. When all film units in the pack are exposed and transported from the camera, the pack ---- containing the battery ---- is discarded.
As alluded to above, the desired performance characteristics of batteries of the type described above are well defined. Essentially, such batteries must be compact and specifically configured for effective integration and assembly with the film pack and at the same time provide the requisite electrical energy for efficient operation of the camera and related accessories until depletion of the supply of film units in the film pack. In addition to the exhibition of adequate capacity characteristics, the flat battery power supply is called upon to have a shelf life or storage capability commensurate with that of the photographic film with which it is intimately packaged. Inasmuch as the batteries are designed to be discarded together with the empty film pack, an economic constraint is involved requiring that they be produced by way of high volume, low cost processes which inevitably dictates the involvment of a high speed, online continuous process capable of efficiently assembling batteries and providing maximum production of acceptable batteries with minimum rejects.
As described in copending application U.S. Pat. Ser. No. 411,254 filed Oct. 31, 1973 entitled "Electronic Photographic System" by E. H. Land and assigned in common herewith, it is highly desirable that the thin flat batteries, while still remaining fabricable at a unit cost permitting them to be discarded, following the expenditure of about 10 film units, be capable of providing the power required to charge the capacitor of an electronic flash unit. This current drain capability should be such as to permit recharging over an extended number of photographic cycles, for instance, the 10 cycles required to expend the film of a package, and provide such charging at a relatively rapid rate. The charging capability for the discardable batteries should be suitable for photographic system energy requirements of, for example, about 100 watt seconds for each photographic cycle, i.e., camera actuation.
From the foregoing, it may be observed that the capability of each discrete battery should be such as to accommodate diverse criteria. For instance, it should provide requisite capacity to meet the complex operational demands of the camera; it should exhibit a storage or shelf life commensurate with that of the film with which it is to be packaged; and it should be adaptable for manufacture using high volume manufacturing techniques at unit costs permitting the highly desirable discardable feature of the film supply-battery supply component of the photographic system. Finally, while remaining thin and compact, it is desirable that the batteries be capable of supplying the energy required of auxiliary devices, for instance, to charge the capacitor of an electronic flash unit at a desirably rapid rate for a necessary number of cycles corresponding with the camera cycles required to exhaust a film unit supply.